Inorganic ligand-protected synthesis and characterization of a {Ag6} cluster within an annular polyoxometalate

Abstract

Silver–polyoxometalate (Ag–POM) complexes, safeguarded by polyoxometalate (POM) ligands, are scarcely documented. Nonetheless, the targeted synthesis of Ag–POMs remains a focal point due to their prospective applications. Here, we successfully obtained an {Ag₆} cluster, characterized as Na₆K₆H₂₅[(P₆W₃₇O₁₂₇){Ag₂(Ag₆O₁₉)}]·53H₂O (1), within an annular polyoxometalate framework via a ligand-protecting strategy in a purely inorganic environment. The hexavacant Dawson-type precursor, [H₂P₂W₁₂O₄₈]¹²⁻, served as a structure-directing as well as a functionalizing unit in the process of synthesis. Proton conducting measurements of {Ag₆} indicated good proton conductivity performance, achieving a conductivity value (σ) of 3.0 × 10⁻² S cm⁻¹ at 368 K and 98% relative humidity (RH). Furthermore, the {Ag₆} cluster demonstrated significant catalytic activity in the selective photoreduction of nitrobenzene.